/*********************************************************************
*
*      Copyright (C) 2001 Andrew Khan
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
***************************************************************************/

package jxl.biff;

/**
 * Class to help handle doubles
 */
public class DoubleHelper {

	/**
	 * Private constructor to prevent instantiation
	 */
	private DoubleHelper() {
	}

	/**
	 * Gets the IEEE value from the byte array passed in
	 *
	 * @param pos
	 *            the position in the data block which contains the double value
	 * @param data
	 *            the data block containing the raw bytes
	 * @return the double value converted from the raw data
	 */
	public static double getIEEEDouble(byte[] data, int pos) {
		int num1 = IntegerHelper.getInt(data[pos], data[pos + 1], data[pos + 2], data[pos + 3]);
		int num2 = IntegerHelper.getInt(data[pos + 4], data[pos + 5], data[pos + 6], data[pos + 7]);

		// Long.parseLong doesn't like the sign bit, so have to extract this
		// information and put it in at the end. (Acknowledgment: thanks
		// to Ruben for pointing this out)
		boolean negative = ((num2 & 0x80000000) != 0);

		// Thanks to Lyle for the following improved IEEE double processing
		long val = ((num2 & 0x7fffffff) * 0x100000000L) + (num1 < 0 ? 0x100000000L + num1 : num1);
		double value = Double.longBitsToDouble(val);

		if (negative) {
			value = -value;
		}
		return value;
	}

	/**
	 * Puts the IEEE representation of the double provided into the array at the
	 * designated position
	 *
	 * @param target
	 *            the data block into which the binary representation is to be
	 *            placed
	 * @param pos
	 *            the position in target in which to place the bytes
	 * @param d
	 *            the double value to convert to raw bytes
	 */
	public static void getIEEEBytes(double d, byte[] target, int pos) {
		long val = Double.doubleToLongBits(d);
		target[pos] = (byte) (val & 0xff);
		target[pos + 1] = (byte) ((val & 0xff00) >> 8);
		target[pos + 2] = (byte) ((val & 0xff0000) >> 16);
		target[pos + 3] = (byte) ((val & 0xff000000) >> 24);
		target[pos + 4] = (byte) ((val & 0xff00000000L) >> 32);
		target[pos + 5] = (byte) ((val & 0xff0000000000L) >> 40);
		target[pos + 6] = (byte) ((val & 0xff000000000000L) >> 48);
		target[pos + 7] = (byte) ((val & 0xff00000000000000L) >> 56);
	}
	
}
